This invention relates to a disc-shaped recording medium constituted by a substrate molded from a synthetic resin and for which information signals are recorded and/or reproduced in a state in which a recording and/or reproducing head is floated with a pre-set gap from a surface of the disc-shaped recording medium on which has been formed a signal recording region. More particularly, it relates to a disc-shaped recording medium having a center clamp mechanism for clamping a disc rotating driving unit, and to a disc drive device employing this disc-shaped recording medium.
Up to now, a magnetic disc employing a substrate formed of glass or metal such as aluminum has been used as a disc-shaped recording medium enclosed in an information processing device such as a personal computer and which is used as a storage device. This magnetic disc is mounted for rotation in unison with a rotating unit by having a rotating unit of the disc rotating driving unit clamped by a center clamping mechanism provided centrally of the disc. The information signals are recorded and/or reproduced on or from a magnetic disc run in rotation in unison with the rotating part of the disc rotating driving unit by a magnetic head supported by a head slider mounted on the distal end of an elastically deformable supporting arm. In recording and/or reproducing information signals on or from a rotationally driven magnetic disc, the magnetic head scans a recording track formed on the signal recording region as the magnetic head is floated at a pre-set gap from the surface carrying the signal recording region.
Meanwhile, the magnetic head scanning this type of the magnetic disc scans the signal recording region of the magnetic disc with a small float from the surface of the magnetic disc carrying the signal recording region. The amount of float of the magnetic head from the magnetic disc needs to be kept constant so that the strength of the magnetic field applied to the magnetic disc or the strength of the magnetic field detected on scanning the signal recording region of the magnetic disc will be constant. On the other hand, a constant amount of float needs to be maintained in order to prevent the magnetic head from colliding against the rotationally driven magnetic disc.
Thus, the magnetic disc needs to be maintained and clamped in a highly accurate horizontal position on the disc rotating driving unit, such that the magnetic disc needs to be assembled in such a condition that the clamp mechanism for clamping the magnetic disc relative to the disc rotating driving unit and the magnetic disc are kept in a horizontal position to high accuracy.
On the other hand, when the magnetic disc is run in rotation as it is clamped to the disc rotating driving unit, the magnetic disc needs to be run in rotation without offset in order to scan the recording track accurately by a floated magnetic head. The clamping mechanism is mounted on the magnetic disc, as the clamping mechanism holds the perimeter of a center aperture of the magnetic disc with a force sufficient to prohibit the magnetic disc from being offset in the direction along the rotational axis and along the radius of the magnetic disc, in order to prohibit the disc from being offset during rotation.
As for a magnetic disc, used as a recording medium for the information processing device, such as a personal computer, such a magnetic disc which employs a substrate molded from a synthetic resin is furnished in large quantities in place of a glass or metal substrate, in order to reduce production cost and in order to enable high-density recording of information signals. In the magnetic disc employing a substrate of synthetic resin, in which a string of pits, such as those for servo signals, can be formed by injection molding, using a stamper, it is possible to produce large quantities of the discs of high recording density inexpensively as compared to the glass or aluminum discs. On the other hand, this sort of the magnetic disc, employing a substrate of synthetic resin, is lower in tenacity than the magnetic disc of glass or aluminum. The magnetic disc, employing a substrate of synthetic resin, tends to be contracted or deformed due to changes in the environmental temperature to which the magnetic disc is exposed. Also, since the magnetic disc is formed by injection molding, thermal contraction occurs on cooling to form projections on the inner or outer rims to affect the planarity of the disc surface.
If a clamp mechanism used for a magnetic disc employing the substrate formed of high-melting glass or metals, such as aluminum, is directly used for the magnetic disc employing the substrate formed of synthetic resin, the following problems arise: First, since the magnetic disc employing the substrate formed of synthetic resin is lower in tenacity than the magnetic disc formed of glass or metals,.such as aluminum, the firstly-stated magnetic disc is locally deformed or warped in a direction along its thickness if a large load is applied by the clamping mechanism in a direction along the rotary axis.
Also, with the magnetic disc employing the substrate formed of synthetic resin, a projection of a minute size is produced on its inner rim provided with the center opening during the substrate manufacture. If the portion formed with the projection is gripped by the clamp mechanism, partial load is applied to the magnetic disc, thus affecting planarity after mounting the clamp mechanism.
Moreover, the magnetic disc employing the substrate formed of synthetic resin undergoes expansion or contraction due to changes in the environmental temperature. At this time, the contact portion between the clamp mechanism and the magnetic disc is subjected to offset due to such expansion or contraction, thus deforming the magnetic disc.
That is, the magnetic disc employing the substrate formed of synthetic resin is subjected to clamp position offset, due to chronological deterioration, even if the clamp mechanism is mounted to high precision, thus affecting the planarity.
In particular, with the magnetic disc on which information signals are recorded to high density, the magnetic head is moved to a position extremely close to the magnetic head during recording and/or reproduction of the information signals on or from the disc. Thus, it may be an occurrence that the magnetic disc collides against the magnetic disc if the magnetic disc is worsened in planarity.
It is an object of the present invention to provide a disc-shaped recording medium formed of synthetic resin in which a clamp mechanism can be mounted, as high planarity of the disc-shaped recording medium is kept, and in which the planarity may be maintained after mounting the clamp mechanism, and a disc drive device employing this disc-shaped recording medium.
It is another object of the present invention to provide a clamp mechanism that is able to clamp a disc-shaped recording medium as the disc-shaped recording medium is maintained in a state of high planarity, and a disc drive device employing this clamp mechanism.
For accomplishing the above objects, the present invention provides a disc-shaped recording medium including a substrate molded from a synthetic resin with a center opening, in which a signal recording region is formed on at least its one surface, and in which information signals are recorded and/or reproduced in a state a rotating recording and/or reproducing head is floated a pre-set distance from the surface carrying the signal recording region. The disc-shaped recording medium includes a clamp mechanism provided with a supporting member arranged on one of the surfaces of the disc-shaped recording medium for supporting the one surface around the center opening and with a thrusting supporting member arranged on the other surface of the disc-shaped recording medium for supporting the other surface around the center opening. The clamp mechanism is mounted on the disc-shaped recording medium as it clamps an area of the disc-shaped recording medium radially outside of the outer perimeter of center opening by at least 0.1 mm. This area is coplanar as each surface of the disc-shaped recording medium carrying the signal recording region.
A disc-shaped recording medium according to the present invention includes, between a contact portion of a thrusting supporting member constituting a clamp mechanism and a disc-shaped recording medium, a load concentration releasing member for releasing the load concentration of the thrusting supporting member.
The clamp mechanism includes, between the supporting member and the thrusting supporting member, an intermediate member arranged in the center opening of the disc-shaped recording medium. There is formed a gap between the intermediate member and the center opening for prohibiting the intermediate member from colliding against the lateral side of the center opening when the disc-shaped recording medium is contracted to reduce the size of the center opening.
A disc drive apparatus according to the present invention includes a disc-shaped recording medium provided with a substrate with a center opening, molded from a synthetic resin, and including a signal recording region formed on at least its one surface, a clamp mechanism including a supporting member arranged on one of the surfaces of the disc-shaped recording medium, by having a center shank passed through the center opening, for supporting an area of the one surface around the center opening, and with a thrusting supporting member arranged on the other surface of the disc-shaped recording medium for supporting an area of the other surface around the center opening. The disc rotating driving mechanism is formed as-one with the clamp mechanism carrying the disc-shaped recording medium for rotationally driving the disc-shaped recording medium, and includes a recording and/or reproducing head for performing recording and/or reproduction as it is floated a pre-set distance from a surface provided with a signal recording region of the rotating disc-shaped recording medium. The clamp mechanism is mounted on the disc-shaped recording medium as it clamps an area of the disc-shaped recording medium radially outside of the outer perimeter of center opening by at least 0.1 mm. This area is coplanar as each surface of the disc-shaped recording medium carrying the signal recording region.